How small are humans? Seeing the position of the earth in the universe, we have to think deeply.

This classic line comes from The Legend of Heroes of the Galaxy, but it tells many people's dreams. But how big is this "sea of stars"? In fact, it has gone far beyond human imagination. In contrast, human beings are really small. Some people may disagree with this view, but we can look back at the earth from some detectors: how small is human? 1972 65438+On February 7th, Apollo 17 took a very shocking photo at a distance of 29,000 kilometers from the Earth, and named this photo: Blue Marbles. Because of the close distance, the land and sea in this photo are still clearly visible. Apollo 8 is orbiting the moon. Astronaut William Anders took out his camera and took equally shocking photos towards the earth. This photo is named: Ground Out. Although the distance between the spacecraft and the earth was not verified when shooting, the average distance between the moon and the earth was 380,000 kilometers, so it is not difficult for us to conclude that this distance is one order of magnitude larger than when shooting "Blue Marbles". Judging from this photo, with the increase of distance, the outline of the earth's surface becomes a little blurred. In 20 17, the detector OSIRIS-Rex took a family photo of the earth and the moon 5 million kilometers away. This distance is an order of magnitude larger than the distance when shooting "Out of the Earth", but at this time, the surface outline of the earth is already very blurred, and the moon is only as big as a "point". So what if we widen the distance a little bit? We might as well look directly at the photos of the earth taken by the farthest detector. Among many detectors, Voyager 1 is the farthest from the earth now. 1 On September 5th, 977, Voyager1was launched. After completing its main task, it flew out of the solar system. It has been nearly 45 years now, and the distance from the earth has reached 23.28 billion kilometers. 1 990 February 14, Voyager1took the last group of photos of planets in the solar system when it was 6.4 billion kilometers away from the Earth. Scientists use computers to make these photos into family portraits of the solar system. Among the family photos, one photo is particularly eye-catching. In this photo, there is only one "bright spot" as big as 0. 12 pixels, and this is our home earth. Carl sagan, a famous astronomer, called this photo a "dim blue dot". This photo is very shocking and even thought-provoking. You know, Voyager 1 has been flying for 32 years after taking this photo, but it still hasn't flown out of the solar system. After this photo was published, it once made people feel fear and despair. After all, human beings have always thought that they are the masters of the universe, but in fact they are so small. What is even more frightening is that scientists estimate that it will take at least 30,000 years for Voyager 1 to fly out of the solar system, which means that the "big" solar system is already astronomical. And only in the solar system, the earth has become almost negligible. So the question is, is the solar system really big enough? Of course not. In fact, the solar system is a very small system. The solar system lies in the spiral arms of Orion in the Milky Way. In the Milky Way, there are about100 billion-400 billion stars like the sun. The total mass of the Milky Way is 1.5 trillion times that of the sun. It takes about 250 million years for the sun to orbit the center of the Milky Way. The solar system is almost negligible to the Milky Way, just as the earth is relative to the solar system. Is the Milky Way galaxy big enough? The answer is obviously not the case. Larger than the Milky Way is a galaxy group (or cluster of galaxies), which is a combination of a group of galaxies. The galaxy group where the Milky Way is located is called the local galaxy group. The galaxy cluster has a diameter of 65.438+0 billion light years, and its total mass is about 65 trillion times that of the sun. There are dozens of galaxies like the Milky Way, such as Andromeda and Magellanic Cloud. Is this galaxy big enough? Not really! The supercluster (or supercluster) is larger than the local cluster, which is located in the middle of virgo supercluster. The diameter of virgo supercluster is 1. 1 100 million light years, and its total mass is about 1 100 million times that of the sun, including about 100 galaxy clusters (or galaxy clusters) similar to our Milky Way, and there are about 47,000 galaxies of the same order as the Milky Way. Virgo supercluster sounds a bit exaggerated. Is it big enough? The answer is still no! Virgo supercluster is a part of Ranyakaya supercluster. There are three supercluster clusters in Rania Kaya, with a diameter of about 520 million light years and a total mass of about 654.38 billion times that of the sun, including about 654.38 million galaxies of the same order as the Milky Way. Is the Ranyakaya supercluster big enough? In fact, the largest known structure in the universe is called large-scale fibrous structure, which can be said to be a supercluster complex. Ranyakaya supercluster is a part of Pisces-Cetacea supercluster complex. The Pisces-Cetacea supercluster complex is about 65.438+0 billion light years long and 65.438+0.5 billion light years wide, and its total mass is about 65.438+0 billion times that of the sun. Although the complex of Pisces-Cetacea supercluster belongs to the large-scale fibrous structure, it is relatively small in the large-scale fibrous structure, and many large-scale fibrous structures are much larger than it, among which the largest is known: Wuxian-Beiguan Great Wall, with the longest end spanning about 65.438+0 billion light years and the other end being 7.2 billion light years. These large-scale fibrous structures are actually located in the Hubble volume, so what is the Hubble volume? According to the results of relativity, the speed limit of matter, information and energy is the speed of light, and the speed of gravitational waves is also the speed of light. The universe was born 65.438+038 billion years ago. Since then, the universe has been expanding. Considering the expansion effect, the largest range that humans can theoretically observe is a spherical space with a diameter of 93 billion light-years centered on the earth. Beyond this range, the light it emits cannot reach the earth for the time being. In the Hubble volume, there are about 2.2 trillion galaxies the same size as the Milky Way. From the perspective of Hubble volume, not to mention the Milky Way, that is, the local group of galaxies, virgo supercluster is very small and can be completely ignored. So Hubble should be old enough, right? Actually, it is not! Hubble volume is not the whole universe, it is only a small part of the universe. The universe is not only much larger than Hubble, but also expanding outward. How big is the universe? The answer is: we don't know yet, but many scientists think that the probability of the existence of the universe is infinite. How to understand this? 1995, Hubble telescope was called to expose the darkest area in the night sky 10 days. Astronomers at that time were very angry because they thought the Hubble telescope was a valuable observation resource, but it was used to do things with no scientific value. So, they are all waiting for jokes. As a result, the scientific research institutions finally published these photos together, which shocked the entire astronomical community at that time. So this area is very dark and small, about the size of a tennis ball 100 meters away. Therefore, there are more than 3000 galaxies like the Milky Way in this photo. This discovery not only has profound scientific connotation, but also this photo was quoted thousands of times later. This photo was later called Hubble deep space. Not only that, but the Hubble telescope also made several similar attempts later, shooting Hubble's deep space and Hubble's ultra-deep space. Among them, the Hubble Ultra Deep Space Project, which was launched in 2003, has about 10000 galaxies similar to the Milky Way. Whether it is Hubble deep space, Hubble deep space or Hubble ultra-deep space, it is actually telling us one thing, that is, no matter which direction the universe looks from the earth, we can't see the edge at a glance, and at the same time, we will find that it seems that every direction is similar, which actually indicates a possibility that the universe may be infinite, and no matter which direction it looks from, the universe is the center. It is likely that human beings are just small in spatial scale. But is the situation really that optimistic? Obviously not! We look at this problem from two levels, one is the material dimension and the other is the time dimension. Let's look at this problem from the material dimension first. Scientists have found that there are actually some substances in the universe that we can't observe. Why can't you observe it? According to this universe, there are four basic interactions, namely, strong interaction, weak interaction, electromagnetic interaction and gravitational interaction. Among them, strong interaction and weak interaction are mainly concentrated in atoms and below, and what we can usually contact is interaction, either gravitational interaction or electromagnetic interaction. The "force" we often say, except gravity, actually belongs to electromagnetic interaction, such as elasticity, friction and so on. The observation of human beings and astronomical equipment also depends on electromagnetic interaction. In other words, if matter does not participate in electromagnetic interaction, then we cannot observe it. In fact, there really are substances (or energy) in the universe that do not participate in electromagnetic interaction. They are dark matter and dark energy. Not only that, with the study of dark matter and dark energy, scientists found that the proportion of visible matter in the universe is actually less than 5%, while dark matter and dark energy account for the majority in the universe, accounting for more than 95%. That is to say, if humans can see and observe, including humans, there are only a few in the universe, but we can't see most of the universe, and we don't even know what each other looks like. From the time dimension, according to cosmology theory, the universe was born in a big bang 65.438+0.38 billion years ago, and then the universe began to expand violently. In other words, the universe has a history of 654.38+03.8 billion years since its birth. If we condense the 65.438+0.38 billion years of the universe into one year, the sun will appear in September of 654.38+0, and the earth will appear on September 2. At 23: 59: 52 on the last day of this year, human civilization was born. At the last second of this year, modern human civilization appeared and science was born. It was at this last second that human beings finally touched some essential problems of the universe through unremitting exploration of unknown fields, sorted out all kinds of knowledge and theories mentioned in this paper, and invented cutting-edge technologies such as airplanes, rockets, atomic bombs and chips. From this point of view, although this second is intermittent, it is wonderful because of human beings. Although human beings are small, they have a heart of the universe. # Spacecraft # # Probe #